Within The Black

Earlier this month, it was revealed by the US Space Command (USSC) that a fast-moving fireball, which exploded over Papua New Guinea 8 years ago, actually originated from outside our solar system - predating the discovery of interstellar visitor 'Oumuamua in 2017.

Whatever remained of this object, if anything, would have ended up falling to the bottom of the ocean.

According to Loeb, something to consider is whether such an object - especially if it has come from interstellar space - has the potential to be a piece of extraterrestrial technology.

Given its small size and the vast area in which it now lies, however, finding it would be a tough ask.
https://www.unexplained-mysteries.com/n ... of-the-sea

I think they say that we've only researched 10% of the Earth's oceans. So if this is true then there's no telling what is out there. Maybe in some deep unexplored area of the sea there's this undiscovered city with life